Ultrasound images are widely used in the fields of biomedical and industrial inspection since they have the characteristics such as non-intrusiveness, real-time imaging and high image quality. Among ultrasound imaging systems, beamformers are the most critical. The so-called beamformer is located at the front end of the system for obtaining the electrical signals of the probe and performing delay control and associated signal processing. The quality of the signals after processing will have a significant impact on the application of the back end of the system, so that the designs of the beamformers are extremely important for imaging systems.
A traditional beamformer consists of two parts: a transmitting end and a receiving end. The transmitting end is used to control the transmission timing of each channel in an array transducer in order to achieve the effects of beam offset and focusing. The receiving end is used to provide receiving focus delay of various channels as well as to perform a delay sum. Since the focus delay of each channel is a function of the change in distance, in order to obtain a higher quality of the image, the value of the focus delay of each channel must be updated dynamically and each channel is given a different weight for adoptive adjustments to improve phase shifts as a result of ultrasound propagates at different speeds in different tissues.
FIG. 1 is a schematic diagram illustrating a receiving end in an imaging system including an array transducer. The receiving end 1 includes an array transducer 10, delay units 11, weighting units 12, and a summing unit 13.
In order to calculate the focus delay of a focal point 14 to a channel at the location (x, 0), the following focus delay equation is used:
            t      rx        =                            (                                                    (                                                                            (                                                                        R                          ⁢                                                                                                          ⁢                          sin                          ⁢                                                                                                          ⁢                          θ                                                -                        x                                            )                                        2                                    +                                                            (                                              R                        ⁢                                                                                                  ⁢                        cos                        ⁢                                                                                                  ⁢                        θ                                            )                                        2                                                  )                                            1                /                2                                      -            R                    )                /        c            ≈                        -                                    x              ⁢                                                          ⁢              sin              ⁢                                                          ⁢              θ                        c                          +                              1            R                    ×                                                    x                2                            ⁢                              cos                2                            ⁢              θ                                      2              ⁢                                                          ⁢              c                                            ,
wherein trx is the focus delay, R is the distance from the focal point 14 to the center point of the array transducer 10, θ is the angle between a line connecting the focal point 14 to the center point of the array transducer 10 and a z axis, and c is the speed of the wave.
However, dynamic focusing of the ultrasound imaging requires a large number of real-time computation and data transmission, and the calculation of which will be extremely complex. As an example, when the weight of each sampling point of a beamformer having 64 channels is calculated, a 64-by-64 matrix transpose operation will need to be carried out. Therefore, when the number of sampling points is increased in order to improve the image quality, its computational complexity will increase rapidly.
From the above, it is known that while the image quality of a traditional beamformer is improved, the number of channels of the array transducer or the number of sampling points of each channel is also increased, thus increasing the computational complexity of the system. Therefore, how to provide a beamformer design that is capable of reducing the computational complexity while maintaining a good image quality is a problem yet to be solved.